zlacker

>>pul+(OP)
> Vertical scaling — a bigger, exponentially more expensive server

This is in practice not true at all. Vertical scaling is typically a sublinear cost increase (up to a point, but that point is a ridiculous beast of a machine), since you're (typically) upgrading just the CPU and/or just the RAM or just the storage; not all of them at once.

There are instances where you can get nearly 10x the machine for 2x the cost.

>>margin+lu
For small consumer products sure, but we're talking at the extreme end of performance and physical capabilities. Sure you can get a 2Ghz CPU for ~2x the price of a 200Mhz CPU, but how much are you going to pay for a 6.0Ghz CPU vs 5.0Ghz? 6.1Ghz vs 6.0Ghz?

>>teawre+gC
Think cores instead of clock speeds.

In the case of cloud instances, doubling cores is frequently less than 100% more expensive.

>>Sohcah+bG
https://aws.amazon.com/msk/pricing/ prices scale linearly with CPU beginning with m5.large, and I wouldn't really want to run a production Kafka on anything less than m5.xlarge. (They do at least keep linearly scaling all the way up.) Speculating wildly, I could probably have run some of our real clusters on the equivalent of a 8xlarge, but of course 32 core systems were not widely available at that time. The cluster I run today, even a hypothetical 48xlarge would struggle.

YMMV for non-managed stuff, but really, you can only bump cores like 3 times realistically, 4 if you started really shitty, before you start getting into special pricing brackets.